1. Field of the Invention
This invention relates to a method and apparatus for deflecting a monochromatic light beam such as a laser beam so as to record a picture or image information on a photosensitive sheet, and to a scanning conversion system for converting a circular scanning line into a linear scanning line.
2. Description of the Prior Art
A system has been developed in which a monochromatic light such as a laser light is modulated and scanned to form a picture or image so as to obtain an apparatus for projecting and displaying the picture or image thereon, and in which the modulated monochromatic light is applied to a photosensitive sheet so as to obtain an apparatus for recording a picture or image thereon. In a method of scanning such a monochromatic light, the use of an electro-optic effect, the employment of an acousto-optic effect, the utilization of a rotatable polyhedral mirror or the use of an electromagnetic type vibration mirror such as a galvanometer has been considered. However, these scanning methods except the method employing a rotatable polyhedral mirror are not suitable from a practical standpoint. Further the deflection angle is generally so large in the scanning device using a rotatable polyhedral mirror that an expensive lens may often be required when a uniform scanning is intended. A light deflecting apparatus using the electro-optic or acousto-optic effect is expensive. A large deflection angle is not obtained, and one problem in such an apparatus is that light point resolution is decreased. In addition, although the scanning device using the electromagnetic type vibration mirror such as the galvanometer may be easily obtained, a very small vibration mirror or many vibration mirrors may be required in practical use when high speed scanning is demanded. In addition, since a saw tooth voltage, a triangle voltage or a phase modulated voltage is required for the driving power source described above, broad-band properties may become important and the driving power source can be complicated.